1. Field of the Invention
This invention relates to a self-polish type antifouling coating composition and particularly to a coating composition comprising a polymerizable metal soap of fatty acid.
2. Brief Description of the Prior Art
Antifouling marine paints are mainly divided into two types, a self-polish type and an insoluble matrix type. The self-polish type antifouling paint can be gradually hydrolyzed and polished by sea water to produce a smooth and fresh surface which reduces the friction between the ship surface and water, thereby decreasing the sailing energy. The fresh surface exposes antifouling toxins contained in the coating until they are used up.
Self-polishing coatings generally comprise a resin containing hydrolyzable groups such as organic acid groups. The rate of hydrolysis of such coatings depends on the type of cation and acid and the percentage of acid groups in the resin.
Self-polishing antifouling coatings may be a toxin-containing type or a toxin-free type. Coatings containing toxins such as organotin are tin substituted polyacrylates which have been popular due to their excellent antifouling properties and self-polishing properties. However, such coatings are subject to legal restriction because of their extreme toxicity. Copper-containing antifouling coatings are less toxic and may incorporate additive toxins if desired. Examples of such coatings are disclosed in JPN Kokai, Tokkyo Koho JP 6,284,168, JP 6,094,471, European Patent Application Nos. EP26,958 and EP204,456. Toxin-free antifouling coatings themselves are not toxic and require additive toxins. Examples of such non-toxic coatings are disclosed in JPN Kokai, Tokkyo Koho, JP 01,131,285, JP 63,314,280 and JP61,218,668.
U.S. Pat. No. 4,774,080 discloses a hydrolyzable antifouling coating composition which has an excellent film-forming property and whose resin is characterized by having at the side chain portions a particular group capable of forming a hydrophilic group through hydrolysis, being hydrolyzed and dissolved in sea water at an appropriate rate and being prepared without the necessity of using a triorganotin compound which is an expensive and toxic material. The particular group at the side chain contains cations of a metal selected from zinc, copper and tellurium. The resin is a linear polymer and forms a non-crosslinked thermoplastic film.